Regenerative braking, coupled with the recent technology advance in hybrid electric vehicles (HEVs) and electric vehicles (EVs), has drawn a lot of attention because of its potential in reducing fuel consumption and emission. Regenerative braking system (RBS) provides HEVs and EVs with capability to recover significant amount of energy during deceleration. For example, when a driver releases the accelerator pedal or depresses the brake pedal, the electric motors in an EV or HEV can be controlled to operate as generators to convert the kinetic and potential energy of the vehicle into electric energy. The recovered electric energy is stored in an energy storage system, typically a battery, for future use.
The amount of energy recoverable and thus the braking torque generated by the RBS are limited by many conditions, including the state of charge (SOC) of the energy storage system. When the SOC is approaching its upper limit, the charging current of the battery decreases and so does the amount of regenerative braking. Conversely, when the SOC is low, the RBS is capable of generating a greater braking torque and is used more frequently by the vehicle. This creates uneven driving experiences and even dangerous driving conditions as the same degree of depression of the accelerator pedal or brake pedal may create different vehicle decelerations at different SOCs. For example, if the driver operates the pedals based on her previous experience, accidents may result because the actual deceleration generated by the RBS may not match the driver's expected deceleration.
The disclosed braking control system is directed to mitigating or overcoming one or more of the problems set forth above and/or other problems in the prior art.